Credentials include identification cards, driver's licenses, passports, and other documents. Credential manufacturing devices process substrates, such as plastic card substrates using one or more processing devices form credential products. Common processes performed by such devices on substrates include, for example, printing processes, laminating processes, and data reading and writing processes.
Printing processes performed by credential manufacturing devices generally operate to print information, such as a photo, account numbers, identification numbers, and other personal information to the substrate. Such printing processes may use a thermal print head and a print ribbon. The print ribbon generally includes a series of colored dye panels (e.g., yellow, cyan and magenta) and a black resin or fusible pigment panel (hereinafter “black resin panel”). The print head includes a line of resistive heating elements, each of which is selectively activated to heat a corresponding portion of one of the panels of the print ribbon and transfer a pixel of print material (i.e., dye or resin) from the panel to the desired surface, such as the surface of the substrate. A wide range of colored pixels may be formed by overlaying pixels of the various colored dyes.
An image is printed to a surface of the substrate by aligning one of the panels of the print ribbon with the substrate, advancing the panel and the substrate past the print head, and heating portions of the panels to transfer pixels of print material to the surface using the print head. These steps may be repeated for other panels of the print ribbon to complete the printing of the desired image on the substrate.
When an image is printed using the black resin panel, a negative of the image remains on the black resin panel due to the removal of the black resin. Such residual images may contain confidential information. As a result, it is desirable to obscure or erase residual images in the black resin panels to eliminate the risk of such information being accessed after the used print ribbon is discarded.